1. Field of the Invention
The present invention relates to a piston packing having a seal function, and more specifically, to a piston reciprocating in a cylinder tube which has the openings at both ends blocked by a pair of end plates, and a structure for mounting a piston packing to such a piston in an improved fitting manner.
2. Description of the Related Art
An actuator such as a rodless cylinder is conventionally employed for example as transfer means for a workpiece.
The rodless cylinder has a pair of end plates coupled to both ends of a cylinder tube in the longitudinal direction and a cylinder chamber is formed in the cylinder tube by blocking the openings at both ends of the cylinder tube therewith. In the cylinder tube, a piston reciprocating along the cylinder chamber is mounted and a slider placed to be movable integrally with the piston is attached on the upper side of the piston.
As shown in FIG. 6, a piston 3 moving along the cylinder chamber 2 of a cylinder tube 1 is fitted with a ring-shaped piston packing 5 along an annular groove 4 cut at the outer circumferential surface. In this case, the bottom surface 6 of the annular groove 4 and the seal surface 7 of the piston packing 5 are brought into close contact so that the entire piston packing 5 is stored in the annular groove 4. Meanwhile, the lip portion 8 of the piston packing 5 slidably comes into contact with the inner surface of the cylinder tube 1.
Note that there is an annular projection 9 serving as a wall to engage the piston packing 5 at one end of the piston 3.
The fitting manner of the piston 3 and the piston packing 5 is not limited to such a rodless cylinder but is universally employed for various actuators or the like reduced to practice which are not shown.
Note however that in the conventional rodless cylinder, the width and depth of the annular groove 4 must be kept at prescribed precision in order to allow the piston packing 5 to smoothly achieve the seal function.
Furthermore, the bottom surface 6 of the annular groove 4 serves as a mounting surface and also seal surface of the piston packing 5, and the wall surface of the annular groove 4 must be smoothed by finishing work in order to maintain the seal function.
In addition, there is a demand for subjecting the piston 3 and the piston packing 5 to mass production, thereby reducing the cost.
A general object of the present invention is to provide a mounting structure for a piston packing which can be subjected to mass production for reducing the cost while maintaining the seal function.